Greenhouse Tasks for this time of year

pitcher plants in greenhouse

I include what should have been done in August (yes, we're not all perfect!) and what we have to look forward to in September. Please remember you can break up this arduous workload with lovely garden visits and events - it shouldn't be work - work -work!


  • Watch for grey mould – if leaves, fruit and flowers are attacked you should destroy affected parts, spray with a systemic fungicide and improve ventilation. Make sure that the plants are not splashed in the evening and never leave old leaves and fruit lying about. Dead-head flowering plants regularly to extend the flowering season.
  • Ventilation remains a vital task. Open all the ventilators and the door on warm days – during the night open only the roof ventilator.
  • Continue with the chore of regular watering. Daily soaking will still be needed for vigorous plants in small containers.
  • Routine feeding of actively – growing plants remains a necessity. Use a potash-rich feed to prolong and improve fruiting and flowering – leave 10-14 days between feeds. Holidays can be a problem – without a helpful neighbour you will need automatic ventilating and watering equipment.
  • This is a good month for taking cuttings for plants in the garden. There are three groups – alpines such as Armeria, shrubs such as Weigela and half-hardy types such as Pelargonium. 
  • The annual round of planting bulbs begins this month – make sure you have an adequate supply of pots, bowls and bulb fibre.
  • It is a good month to reflect on successes and failures to learn for next years plans. You can also be collecting and storing some of your own seed over the next few weeks.


Temperature has to be carefully controlled this month. In an Indian summer you will have to open up all the ventilators and perhaps the door to avoid overheating, but during a cold snap all the ventilators should be closed. Aim to keep the temperature in the 50o – 70oF range – close down the ventilators in early evening to retain some of the sun’s warmth overnight.

  • Damping down as well as ventilation are reduced this month. Only spray the floor and staging on warm days and even then make sure that the job is completed by midday.
  • Compost stays moist longer as temperatures fall – growth becomes less active. Reduce the frequency of watering accordingly. Keep watch for fungal diseases which tend to appear this month.
  • Your blinds will be used less and less in September – maximum light is now more important than heat control but maintain some form of shading in areas where shade-lovers such as ferns are present.
  • There may be a gap between clearing out the tomatoes and cucumbers and bringing in the frost-sensitive plants from outside. This may be at the end of this month or the beginning of October and is an excellent opportunity to have a thorough clean inside the greenhouse.
  • Don’t wait too long before bringing in tender specimens – one sharp frost may kill them. Make sure that the pots of chrysanthemum, fuchsia etc are free from pests before the move indoors.
Tags: alitex, greenhouse growing